The present invention relates to an intraocular lens structure or pseudophakos designed to be placed in either the anterior or posterior chamber of the eye after the removal of a natural lens as a result of a cataract condition.
It has been found that the insertion of an intraocular lens is by far the best solution to correcting vision after cataract surgery. The proper placement of an intraocular lens always involves the risk of damage to the eye during the insertion process as well as at a later time period if the intraocular lens dislocates.
Prior intraocular lens structures have employed the use of the iris to fix the same. In this regard references made to U.S. Pat. No. 3,906,551 issued to Otter, U.S. Pat. No. 3,922,728 issued to Krasnof, U.S. Pat. No. 4,085,467 issued to Rainin et al as examples of this system of fixation. Although this type of lens structure has been quite successful it is generally believed that proper insertion requires greater than average skill on the part of the eye surgeon performing this work.
Recently there have been a family of intraocular lenses which are simply wedged between opposite sides of the eye chamber in the vicinity of the iris. Such lenses were an off-shoot of an early development by Strampelli, who devised such a lens in 1953. Generally this type of lens must be perfectly sized to avoid dislocation and a reentry to the eye by the surgeon for relocation of the lens or insertion of a new lens. It has been found that the wedging type intraocular lens may be placed in the anterior chamber of the eye and fixed by the anterior chamber angle. Likewise, this lens may be placed in the posterior chamber and held in place at the ciliary sulcus. Early designs of wedging type lenses include the Barraquer lens which includes at least one springy leg. The resilience of this leg offers a degree of adjustment and greatly reduces the possibility of dislocation during the postoperative time period. Although originally designed for postioning within the anterior chamber, recent modifications to the Barraquer lens, eg: the Shearing lens, permit posterior chamber fixation as well. At least one design of the Shearing lens employs a pair of springy legs attached to the lens. One resilient leg of the Shearing lens is placed through a chemically dilated pupil to the area of the ciliary sulcus. The second resilient leg is coiled and forced through the pupil with the lens to the posterior chamber. The second resilent leg is released and directed toward the ciliary sulcus at a position therein opposite to that of the first resilient leg. The Shearing lens may be used with extra capsular surgery only since a secondary support, by the remaining portion of the natural lens, is necessary if good fixation at the ciliary sulcus is not achieved. In addition, insertion of the Shearing lens may result in severence of the zonule which would allow the Shearing lens to travel into the vitreous humor behind the iris. Along these lines, maximum pupil size is desirable to insure proper fixation. Adequate dilation of the pupil is not possible in every case. Moreover, the releasing of the second resilient leg creates a whip-like action which can tear the iris resulting in bleeding and damage to the eye. All in all, posterior fixation of the Shearing lenses is difficult to predict.
There is a need for a wedging type lens which may be easily fixed into the posterior or anterior chamber of the eye which offers a secondary means of support, without substantial damage to the eye during and after insertion.